Detailed Explanation of Cooling Tower Technology

2025-05-07

I. Basic Introduction
The cooling tower is a comprehensive product that integrates many disciplines such as aerodynamics, thermodynamics, fluid mechanics, chemistry, biochemistry, materials science, static and dynamic structural mechanics, and processing technology. The water quality is a function of multiple variables, and the cooling is a comprehensive process of multiple factors, multiple variables, and multiple effects. With the continuous development of the cooling tower industry, more and more industries and enterprises are using cooling towers, and many enterprises have also entered the cooling tower industry and developed.
II. Product Principle

In the circulating water system of the cooling tower, there must be a certain "surplus energy of 20%-25%". During operation, this energy will be gathered at a certain valve. Over time, this energy will be wasted. The external water turbine utilizes this "surplus energy" to convert it into high-efficiency mechanical energy, thus completely replacing the cooling tower fan motor to achieve the purpose of power saving.
The key for the external water turbine to achieve the driving efficiency of the motor lies in: understanding the surplus energy in the design of the cooling tower circulating water system, and at the same time, the design of the impeller of the water turbine is also crucial.
The composition of the surplus energy mainly consists of the following 6 parts:

The margin value that must be considered in the design of the circulating water system;
The potential energy utilization of the heat exchange equipment;
The self-adjusting ability of the water turbine;
The kinetic energy conversion efficiency of the circulating water system;
The energy consumed by the valve when it is not fully opened;
Meeting the system requirements by combining and then diverting the low flow rate.

Energy-saving Retrofit of Existing Cooling Towers
The circulation between the cooling tower and the heat exchange equipment is driven by a water pump. The external water turbine uses the pressure energy of the return water to convert and drive the water turbine to do work and drive the fan. Generally, energy-saving retrofitting is carried out for three cooling towers. In the design, the flow rate is on the large side, and the actual usage is about 60%. Considering the changes in production requirements, the energy-saving retrofitting method is: two towers are driven by water turbines, and one tower is driven by a motor as a backup during the summer period.
Design of New Cooling Towers
The key point of the work of the external water turbine is that the return water pressure or return water flow rate can meet the working capacity of the water turbine to drive the fan. According to the law of conservation of energy - how much return water flow rate or pressure conversion = how much fan speed. The speed of the external water turbine increases or decreases according to the increase or decrease of the system flow rate. For this system with three external water turbine cooling towers, the outlet pipes of the water turbines of the three towers are connected, and the flow rate can be adjusted through the bypass valve, which is convenient for maintenance.

III. Product Structure
As the name implies, the main equipment of the external water turbine cooling tower is the water turbine installed outside the wind cylinder of the cooling tower. The main components of the external water turbine are a 304# stainless steel impeller, a 316L stainless steel main shaft, and the volute main body is made of carbon steel. The guide impeller is an important component for energy conversion. Before the circulating water enters the impeller, a swirling flow is generated when passing through the guide impeller, which further improves the energy conversion efficiency of the impeller. The foundation of the water turbine consists of two steel plates of 900*900 on the upper and lower sides, and double-headed bolts are used to adjust the position (convenient for maintenance and repair). The weight design of the water turbine is similar to that of the traditional motor weight, and it is matched with the soft connection of the reduction gearbox transmission inside the wind cylinder, etc.
For the external water turbine of the cooling tower, since it is installed at the position of the motor outside the wind cylinder of the cooling tower, there is no space limitation. The diameter, number of blades, shape, and angle of the impeller of the external water turbine can be enlarged in design according to the actual situation of customers, and the torque can be increased to improve the conversion efficiency. Through the design of systems with different flow rates and pressures, the most perfect transmission conversion ratio can be achieved, so that the rotation speed of the cooling tower fan is greater than or equal to that of the fan driven by the original motor. The snail shape of the external water turbine adopts the bionics snail effect to reduce the impact force and vibration rate of the circulating water.
IV. Application Information
Cooling towers are mainly applied in the fields of air conditioning cooling systems, refrigeration series, injection molding, leather making, foaming, power generation, steam turbines, aluminum profile processing, air compressors, industrial water cooling, etc. The most widely used applications are in the air conditioning cooling, refrigeration, and plastic chemical industries. The specific classification is as follows:
A. Air room temperature regulation category: air conditioning equipment, cold storage, refrigeration chambers, refrigeration, air conditioning for heating and cooling, etc.;
B. Manufacturing and processing category: food industry, pharmaceutical industry, metal casting, plastics industry, rubber industry, textile industry, steel mills, chemical industry, petrochemical products, etc.;
C. Mechanical operation cooling category: generators, steam turbines, air compressors, hydraulic presses, engines, etc.;
D. Other industries...
The function of the cooling tower is to conduct heat exchange between the cooling water carrying waste heat and the air inside the tower body, so that the waste heat is transferred to the air and dissipated into the atmosphere.
V. Principle
General Terms
The term "cooling tower" is used to describe direct (open circuit) and indirect (closed circuit) heat dissipation equipment. Although most people think of a "cooling tower as an open direct contact heat dissipation device", the indirect cooling tower, sometimes called a "closed-circuit cooling tower", is also a cooling tower.
A direct or open-circuit cooling tower is a sealed structure inside which the circulating water is sprayed onto the fiberglass filler in a spray manner. The filler provides a larger contact surface, and the heat exchange effect is achieved through the contact between water and air. Then, the fan drives the air circulation inside the tower, and the hot air flow after heat exchange with the water is carried out, thus achieving cooling. The filling may include multiple, mainly vertical, wet surfaces on which the water spreads (filling) or horizontal splash elements that create a cascade of several layers of small water droplets with a large surface area (splash).
Indirect or closed-circuit cooling towers do not involve direct contact between the air and the liquid, usually water or a mixture of water and ethylene glycol being cooled. Different from the open cooling tower, the indirect cooling tower has two independent fluid circuits. One is the water in the external circuit, which is in the second circuit and is connected to the heat fluid process to be cooled through the outer circulation of the tube bundle (non-open coil) and returns in a closed circuit. The air is drawn through the cascade water outside the entire heat pipe, providing similar evaporative cooling as the open cooling tower. During operation, the heat flow moves from the internal fluid circuit, through the tube wall of the coil, to the external circuit, and then is heated by the air and some evaporation of water and dissipated into the atmosphere. The operation of the indirect cooling tower is therefore very similar to that of the open cooling tower with one exception. In this process, the coolant is in a "closed" loop and is not directly exposed to the atmosphere or the external circulating water.
In a counterflow cooling tower, the air moves upward through the filler or tube bundle while the water moves downward in the opposite direction.
In a crossflow cooling tower, the air moves horizontally through the filler while the water moves downward.
Another characteristic of the cooling tower is that the mechanical ventilation cooling tower is more commonly used, which relies on an electric-driven fan to attract or force air in. The natural ventilation cooling tower uses a taller exhaust chimney to provide buoyancy for the air, and the fan assists the natural wind to increase the effect of buoyancy. Many early cooling towers relied on the buoyancy generated by the wind direction to attract air. If the cooling water is reused from the cooling tower, some water must be added to replace or replenish the part of the water that has evaporated. Since evaporation involves pure water, the concentration of dissolved minerals and other solids in the circulating water tends to increase unless some solids are dissolved. Then, some water is also lost as droplets in the exhaust gas (drift), but this is usually reduced to a very small amount. For this reason, a baffle device, called a drift eliminator, is installed to collect the droplets. The evaporation of the cooling water, the blowdown, and then the drift reduce losses such as wind blowout and other water leakage, maintaining a stable water level.
VI.
Common Terms
Some useful terms commonly used in the cooling tower industry:
Drift
The water droplets carried out with the exhaust gas of the cooling tower. The drift droplets have the same impurity concentration as the water entering the tower. The drift velocity is usually reduced by using baffle-like devices, so-called drift eliminators, after traveling through the air and must leave the filling and the spray area of the tower.
Blowout
The water droplets blown by the wind in the cooling tower, generally at the air inlet opening. Water may also be lost due to splashing or spraying in the case of wind. Devices such as wind curtains, louvers, splash deflectors, and water flow regulating devices are used to limit these losses.
Plume
The saturated air flow leaving the exhaust gas of the cooling tower. The plume is visible water vapor, which contains the condensation of cool air upon contact, similar to the fog exhaled by a person in very cold weather.
Saturated Air
In some cases, the cooling tower may pose the hazards of spraying or icing to it and its surrounding areas. It should be noted that the evaporation cooling process of water is "pure" water, as opposed to the very small proportion of drift droplets or water blown inside the air inlet.
Blowdown
The blowdown of the circulating water flow is the amount removed to maintain the dissolved solids and other impurities at an acceptable level. The leaching caused by the flushing action of the water flowing through the wooden structure cooling tower - the loss of wood preservative chemicals.
Noise
The sound energy emitted by the cooling tower and heard (recorded) at a given distance and direction. The sound is affected by the impact generated, the decline in water quality, the movement of the air affected by the fan, and the movement in the fan blade structure, motor, gearbox, and transmission belt.
Hazard
After long-term use, the cooling tower will breed bacteria, and the typical bacteria is "Legionella". This bacteria can cause infectious diseases, and an area within 800 meters around each cooling tower will be affected. The cooling towers in the city are a major source of urban pollution. Legionella is spread through the air. The water tank of the air conditioning system is an ideal breeding place for Legionella and can spread throughout the building through the pipes. Therefore, people who stay in an air-conditioned room for a long time should be particularly careful.